The invention relates to batteries.
Batteries, such as alkaline batteries, are commonly used electrical energy sources. Generally, a battery contains a negative electrode, typically called the anode, and a positive electrode, typically called the cathode. The anode contains an active material (e.g., zinc particles) that can be oxidized; and the cathode contains an active material (e.g., manganese dioxide) that can be reduced. The anode active material is capable of reducing the cathode active material. In order to prevent direct reaction of the anode material and the cathode material, the anode and the cathode are electrically isolated from each other by a separator.
When a battery is used as an electrical energy source in a device, such as a cellular telephone, electrical contact is made to the anode and the cathode, allowing electrons to flow through the device and permitting the respective oxidation and reduction reactions to occur to provide electrical power. An electrolyte in contact with the anode and the cathode contains ions that flow through the separator between the electrodes to maintain charge balance throughout the battery during discharge.
Some devices, such as digital cameras and cellular telephones, can demand high power from batteries. In such applications, it is desirable for the batteries, e.g., primary alkaline batteries, to have good performance and long lifetimes at high current discharge.
The invention relates to using stepped potential electrochemical spectroscopy (xe2x80x9cSPECSxe2x80x9d) to select a manganese dioxide for high current discharge batteries. The SPECS results yield a dimensionless parameter, termed herein the xe2x80x9cpower coefficientxe2x80x9d , which can be used to predict the high current discharge performance of a cathode material.
Preferably, a high current discharge MnO2 has a power coefficient greater than 3.6, preferably greater than about 3.8, and more preferably greater than about 4.0 or about 4.2. As used herein, manganese dioxide, or MnO2, refers to a xe2x80x9cnominalxe2x80x9d manganese dioxide, or MnO2xe2x88x92x, where 0xe2x89xa6xxe2x89xa60.1. An example of manganese dioxide is gamma-MnO2, an intergrowth of pyrolusite and ramsdellite used in batteries.
The invention also relates to batteries, such as primary alkaline batteries, LeClanche cells, and ZnCl2 cells, having cathodes including the manganese dioxide described above. The cathodes can further include carbon particles and a binder. The batteries can include an anode having zinc as the active material.
Other features, objects, and advantages of the invention will be apparent from the drawings, description, and claims.